wtf is going on??

okay so recently my 18 is going cray... when it good hit in a song goes it makes a weird popping sound... and sometimes with no reason it just starts going crazy and making weird effing sounds.... I checked the t joint and the spider landing and they are both intact... all grounds are good speaker wires are good, amp is fine. Idk what is going on... it only goes crazy on full vol... almost like its unloading but it never did it until recently when I pulled it out to finish the box and put it back in... help?